Fluid-pressure-producing device



Aug. 15, 1939. o, H. FOWLER 2,169,524

FLUID-PRESSURE PRODUCING DEVICE Filed Dec. 18, 1957 3 Sheets-Sheet l F Z INVENTOR, 5 BYOms-Aff?! Forme-e ATTORNEY Aug. l5, 1939. o, H, FQWLER 2,169,524

FLUID-PRESSURE PRODUCING DEVICE Filed Dec. 18, 1957 3 Sheets-Sheet 2 hATTORNEY Aug. 15, 1939. o, H, FQWLER 2,169,524

FLUID-PRESSURE PRODUCING DEVICE Filed DeG. 18, 1957 3 SheebS-Sheel 3 INVENT OR.

ATTORNEY Patented Aug. 15, 1939 UNITED STATES Pli'rlazN'rv OFFICE FLUID-PRESSURE-PRODUCIN G DEVICE poration of California.

Application Decihnber 18, 1937, Serial N0. 180,627

10 Claims. (Cl. (Hl-54.5)

'I'his invention relates to fluid pressure producing devices.

Broadly the invention comprehends a fluid pressure producing device for operating separate braking systems, one for actuating the brakes associated with the front wheels of a vehicle, and anotherI for actuating the brakes associated with the rear wheels of the vehicle.

An object of the invention is to provide a duplex fluid pressure producing means, a single actuator for operating the pressure producing means in unison, means compensating for a differential of pressure in the pressure producing means, and means for maintaining one of the pressure producing means operative in the event of failure of the other.

A feature of the invention is a cylinder having therein an actuating piston, a floating piston dividing the cylinder into two chambers each connected to a pair of brakes, means intermediate the pistons operative after the maximum allowable effective movement of the actuating piston to cause the pistons to move in unison, and a stop for limiting the movement of the floating piston.

Another feature of the invention is an actuating piston and a floating piston, and a spring interposed between the pistons supporting a thrust member.

Other objects and features of the invention will appear from the following description taken in connection with the drawings forming a part of this specification, and in which:

Fig. 1 is a diagrammatical illustration of a iiuid pressure braking system embodying the invention;

Fig. 2 is a vertical sectional view of the fluid pressure producing device illustrating the pistonsA in the position of rest; c

Fig. 3 is a fragmentary view illustrating the pistons at the end of the effective stroke of the actuating piston;

Fig. 4 is a cross-sectional view substantially on line 4-4, Fig. 2;

Fig. 5 is a cross-sectional view substantially on line 5-5, Fig. 2;

Fig. 6 is a fragmentary view illustrating a modified form of the invention; and

Fig. '7 is a fragmentary view .illustrating another modied form of the invention.

Referring to the drawings for more specific details of the invention, I0 represents generally a fluid pressure producing device including a reservoir I2 having two compartments I4 and I I5 communicating with one another as at I8. The

reservoir has a filling opening 20 normally closed as by'a plug 22, and the plug is provided with openings '24 for venting the reservoir to the atmosphere.

A cylinder 2'6 formed at the base of the resero voir has one of :its ends closed as by a head 28 having an inwardly extending projection 30, the object of which will hereinafter appear. The cylinder has spaced ports 32 and 34, communicating with the compartment I4 of the reservoir, and a discharge port 36 controlled as by a twoway valve 38. The cylinder also has spaced ports 40 and 42, communicating with the compartment i6 of the reservoir, and a discharge port 44 controlled as by a two-way valve 46.

A fluid pressure delivery pipe or conduit 48 connected to the two-way valve 38 has branches connected respectively to fluid pressure actuated motors 50 arranged for the actuation of the friction elements of a pair of brakes, and, correspond- 20 ingly, a uid pressure delivery pipe or conduit 52 connected to the valve `46 has branches connected respectively to fiuidpre'ssure actuated motors 54 arranged for the actuation of the friction elements of another pair of brakes.

Preferably the fluidfpressure'actuated motors are arranged in pairs, :one pair for actuating the friction elements of the brakes associated with the front wheels of a,vehicle, and another pair for actuating the friction elements of the brakes associated with the rear wheels of the vehicle.

The brakes may be of conventional type including a.' xed support or backing plate 56 adapted to be secured to an axle housing or to an axle, a rotatable drum 58 associated with the backing plate adapted to be secured to a wheel, a pair of corresponding interchangeable friction elements or shoes B0 and 62 pivoted on the backing plate, a retractile spring 64 connecting the shoes, anda motor corresponding to the motors 50 and 54 mounted on the backing plate between the shoes and 62 and operative to actuate the shoes .into engagement with the drum 58 against the resistance of the retractile spring 64.

A`piston 66, reciprocable in the open end of the cylinder 26, is retained against displacement by a washer 68 seated on an annular shoulder in the open end of the cylinder and secured in place by a retaining ring 10 seated in a groove in the wall of the cylinder. 'I'he piston has a head 12, a body portion 14, and a skirt 16. The skirt has fitted thereon a sealing cup 18 for inhibiting seepage of iiuid from the cylinder past the piston; the body 14 is reduced in cross-section so as to provide, in conjunction with the wall of the cylinder, an annular chamber 80 communicating with the compartment |4 of the reservoir by way of the port 82; and the head 12 of the piston has a plurality of spaced passages 82 therethrough providing communications between the annular chamber 80 and that portion of the cylinder forward of the piston. A collapsible sealing cup 84 supported on the head of the piston controls the passages.

A recess 86 in the body of the piston 66 receives one end of a thrust pin 88 having on its other end a coupling 90 connected by a flexible boot 82 to the open end of the cylinder 26 for thel exclusion of dust and other foreign substances, and avrod 94 connects the coupling to a foot pedal lever 86 pivotally mounted as at 88 and connected as by a retractile spring |00 to a xed support |02.

A floating piston |04 is fltted for reciprocation in the cylinder 26 between the discharge ports 86 and 44, and divides the cylinder 26 into two chambers |06 and |08, one constituting that portion of the cylinder forward of the piston 66, and

4the other constituting that portion of the cylinder forwardof the floating piston |04. This floating piston has a head ||0 on one of its ends and a head ||2 on its other end. The piston also has a reduced body portion ||4 providing, in commotion with the wall of the cylinder, an annular chamber ||6 communicating with the compartment I6 of the reservoir by way of the port 40, and mounted in the wall of the cylinder is a stop I8 extending into the chamber ||6 and adapted to support the piston |04 when in its retracted position.

The head ||0 of the floating piston has a plurality of 'spaced passages |20 therethrough providing communications betweeny the annular chamber ||6 and the chamber |08, or that portion of the cylinder forward of the floating piston. A collapsible sealing cup |22vsupported on the head ||0 controls the passages |20, and a spring seat |24 suitably secured'in the bottom of the cup receives one end of a spring |26. having its other end sleeved on the extension 80 and seated on the head 28. The spring seat |24 is preferably slightly heavier than the conventional, so that at the end of the maximum allowable stroke of lthepiston the spring seat may abut the extension I0 and support the piston without injury to the sealing cup |22.

Supported on the back of the head I|2 of the floating piston is a sealing cup |28 for inhibiting seepage of fluid from the annular chamber H6, past the head I I2, andsupported on the head I I2 is a sealing cup |80 for inhibiting seepage of fluid from the chamber |06 past the head H2.

The sealing oups 84 and |30 have suitably secured in their respective bottoms relatively heavy spring rests |82 and |84, and interposed between these seats is a return spring |36 for the actuating piston. A sleeve |88 fltted on the spring is adapted to engage the respective spring rests |32 and |34 upon attaining the'maximum allowable movement oi the actuating piston 66. The sleeve has a central flange |40 provided with a thread or groove |42 of a different pitch than that of the convolutions of the spring, so that when the,`

sleeve is fitted on the spring, with at least one convolution of the spring in the groove, -there is provided a bindingA action between the spring and the sleeve, serving to retain the sleeve in a centralized position with respect to the overall length of the spring.

A modification of the return spring and the sleeve is illustrated in Fig. 6. In this embodiment, the sealing cups 84 and |30 have suitably secured in their respective bottoms fairly heavy spring seats |44 and |46, each having ytongues |48 struck therefrom so as to enter the respective ends of a spring |50 interposed between the seats. A sleeve |52 has an internal flange |54 substantially centrally of its length, and this flange has a thread or groove |56 of a different pitch than that of the convolutions of the spring, so that when the sleeve is threaded on the spring there lwill be provided a clamping action between the spring and the sleeve, serving to retain the sleeve centrally of the spring. In this modifled form of the invention, the respective ends of the sleeve abut the spring rests |44 and |46 upon attaining the maximum allowable movement '5f the actuating piston.

Another modiflcation of the return spring and sleeve is illustrated in Fig. 7. In this embodiment of the invention, the sealing cups 84 and Y have suitably secured in their respective bottoms heavy spring seats |58 and |60. A sleeve |62, positioned in the cylinder, has arranged centrally thereon a circumferential flange |64, and

sleeved on the respective ends of the sleeve mediate the flange |64 and the respective spring seats |58 and |60 are return springs |66 and |68.

In a normal operation, assuming that the system is properly installed and filled with suitable fluid, upon depressing the foot pedal lever 96 to apply the brakes, force is transmitted from the lever, through the rod 84 and thrust pin 88, to the piston 66, resulting in movement of the piston on its compression stroke. During the initial movegization of the motors 60, and resulting in move-- ment of the shoes 66 against the resistance of the retractile springs 64 into engagement with'- the drums 58.

Concomitantly with the operation hereinabove described, the fluid under pressure in that portion of the cylinder forward of the piston 66, or in the chamber |06, imposes pressure on the head ||2 of the floating piston I 04, resulting in movement of this-piston on its compression stroke. During the initial movement of the floating piston |04 on its compression stroke, the sealing cup |22 on the head ||0 of the piston closes the port 42, and, thereafter, as the piston advances on its compression stroke, pressure is imposed on the fluid ln that portion of the cylinder forward of the head |0 of the piston |04, or in the chamber |08, resulting in displacing fluid from the chamber |08, through the port 44, past the twoway valve 46, and through the fluid pressure delivery pipe or conduit into the fluid pressure actuated motors 54, causing energization of thev motors 54 and resulting in movement of the shoes 60 connected to these motors against the resistance of the retractile springs 64 into engagement with the drums 58.

Under normal conditions. variations of pressure may be produced in the respective chambers |06 and |08, due to a differential in the ad- Justment of the respective pairs of brakes asso- 1 to their retracted positions.

ciated with the front and rear wheels of the vehicle, and movement of the floating piston |04 compensates for this differential of'pressures so that both pairsof brakes may be applied with equal force and effect.

Upon release of the foot pedal lever 86 at the conclusion of a. braking operation, the lever is returned to its retracted position under 'the influence of the retractile spring |00, and retracts the rod 84 connected to the lever and the thrust pin 88 connected to the rod. This results in release of the piston 66, accompanied by release of pressure on the iluid in the cylinder, and,' consequently, release of the piston |04. Upon release of the pistons 66 and |04, the return springs |26 and |36 become effective to return the pistons As the pistons 66 and |04 return to their retracted positions, partial vacuums are created in the chambers |06 and |08. This results in drawing fluid fromY the compartments i4 and I6 of the' reservoir, through the ports 32 and 40, into the annular chambers B0 and H6, thence through the passages 82 in the head of the piston 66, past the cup 84, into the chamber |06, and through the passages |20 in the head of the piston ||0 past the cup |22 into the chamber |08, completely filling the chambers |06 and |06.

During this period fluid is returning to the chambers |06 and |08 from the fluid pressure actuated motors 50 and 54, and the fluid pressure delivery pipes i8 and 52 connecting the motors to the chambers |06 and |08, under the influence of the retractile springs connecting the friction elements of the respective brake structures. Under these conditions, the chambers |06 and |08 receive fluid in excess of that required to fill the cylinders, and such excess fluid is returned to the reservoir by way of the compensating ports 3d and 42.

The maximum allowable effective movement of the pistons 66 and |06 is substantially seven` eighths of an inch each. '1111s movement of the pistons is adequate to displace sumcient volume of fluid from the chambers |06 and |08 through the discharge ports thereof and the lhuid pressure delivery pipes connected to the discharge ports into the fluid pressure actuated motors to effec-v tively actuate both sets of brakes, and any slight differential of pressures created in the chambers |06 and |06 is compensated for by movement of the :doating piston ile so as to equalize the brakes.

In the event of failure of the braking system for actuating the brakes associated with the front wheels of the vehicle, the actuating piston 66 moving on its compression stroke depresses the return spring |36 sufliciently to seat the respective ends of the sleeve |38 carried by the spring on the spring seats |32 and |34 in sealing cups 84 and |34 on the heads of the actuating piston 66 and floating pistons ||4, and, thereafter, the pistons move as a single unit. The actuating piston 66 is non-effective, except for the transmission of force therefrom through the sleeve |38 to the floating piston |30, and the iloatinty piston is actuated with the same effectiveness as in a normal operation wherein it is actuated by pressure on the fluid between the pistons.` In subsequent operations, the piston 66 remains ineffective for producing pressure on the fluid in the chamber forward thereof, but serves merely as a mechanical means for actuating the floating piston which operates as under normal conditions.

In the event of failure of the braking system for actuating the brakes associated with the rear wheels of the vehicle, the floating piston, moving on its compression stroke, compresses the return spring |26 sufficiently to seat the concentric extensions on the head 28 of the cylinder on the spring seat |24 in the sealing cup |22 on the head I I0 of the floating piston so as to retain the piston against furthermovement. During this movement'of the floating piston, the actuating piston, having followed through, maintains a pressure on the fluid forward thereof, and hence in the braking system actuated thereby. In subsequent operations, the floating piston is moved by fluid under pressure to its seat on the extension 30 as the actuating piston 66 advances on its compression stroke, and is held on its seat by the pressure on the fluid between the pistons, to the end that the braking system for the front wheels maybe actuated as under normal conditions. f

Although this invention has been described in connection with certain specific embodiments, the principles involved are susceptible of numerous other applications that will readily occur to persons skilled in the art. The invention is, therefore, to be limited only by the scope of the appended claims.

Having thus described the various features of the invention, what I claim as new and desire to secure by Letters Patent is: i

1. A fluid pressure producing device comprising a reservoir having two compartments, a cylinder having ports communicating with the respective compartments and spaced discharge ports, a piston reciprocable in the cylinder, a floating piston in the cylinder between the discharge ports, a spring interposed between the piston and the floating piston, and a sleeve supported on the spring.

2. A fluid pressure producing device comprising a reservoir having two compartments, a cylinder supplied from the reservoir having one end closed and its other end open and spaced discharge ports, an actuating piston in the open end of the cylinder, a floating piston in the cylinder between the discharge ports, a spring between the closed end of the cylinder and the floating piston, a spring between the oating piston and the actuating piston, and a sleeve supported on the lastmentioned spring.

3. A fluid pressure producing device comprising a reservoir having two compartments, a cylinder supplied from each of the compartments having spaced discharge ports, a head on one end of the cylinder having an extension projecting into the cylinder, an actuating piston reciprocable in the open end of the cylinder, means on the actuating piston for controlling the flow of fluid from one of the compartments to the headr of the piston, a floating piston in the cylinder between the discharge ports, means on the floating pistonfor controlling the flow of fluid from the other compartment to the forward head of the floating piston, a spring between the head and the floating piston embracing the extension on the head, a spring between the floating piston and the actuating piston, and a sleeve threaded on the lastmentioned spring.

4. A fluid pressure producing device comprising a cylinder, spaced pistons movable therein, a spring interposed between the pistons, and a sleeve supported on the spring.

5. A uid pressure producing device comprising a cylinder, spaced `pistons movable therein, a

spring interposed between the pistons, and a sleeve threaded on the spring..

6. A iiuid pressure producing device comprising a reservoir, a cylinder supplied therefrom, spaced pistons movable in the cylinder, a coiled spring interposed between the pistons, and a sleeve in the spring having a part interlocked therewith.

'7. A fluid pressure producing device comprising a reservoir, a cylinder supplied therefrom, spaced pistons movable in the cylinder, a spring interposed betweenl the pistons, and a sleeve on the spring having a flange provided with a groove receiving at least one of the convolutions of the spring.

8. A fluid pressure producing device comprisl ing a reservoir, a cylinder supplied therefrom, spaced pistons movable in the cylinder, a coiled spring interposed between the pistons, a sleeve telescoping the spring, a ilange on the sleeve having a groove of a different pitch than the pitch of the convolutions of the spring and receiving at least one of the-convolutions of the spring.

9. A uid pressure producing device comprissarcasm ing a reservoir, a cylinder supplied therefrom. spaced pistons in the cylinder, sealing cups supported on the heads of the pistons in oppositely disposed relation to one another, spring seats secured in the cups, a coiled spring interposed between the seats, a sleeve telescoping the spring,

a ilange on the sleeve? having a groove of a diierent pitch than the pitch of the convolutions of the spring and receiving at least one of the` convolutions of the spring.

10. A iluid pressure producing device comprising a reservoir, a cylinder supplied therefrom, a`

floating piston in the cylinder dividing'the cylinder into two chambers each having a discharge port, means limiting movement of the floating piston, a return spring for the iloating piston, an

` actuating piston in the cylinder, means for mov- OWEN H. FOWLER. 

